The standard optical microscope, used routinely in biology, medicine and semiconductor processing, is large. Typically, samples of tissue are observed in vitro after being mounted on a microscope slide. Such microscopes are not suitable for in vivo observations of the skin or internal organs of the human body; they are just too large. Consequently, there is a need for a small microscope which could be used for observations of melanomas of the skin, and the teeth and gums, and for endoscopy of cells inside arteries and veins and organs of the body. Ultimately, if such a microscope could be mounted inside a hypodermic needle, it would be suitable for taking in vivo biopsies and for observing microscopic features of the body, such as the flow of blood and plasma in veins, arteries, and other vessels of the body, the fluid in tear ducts, and the general condition of small vessels. Although we have described biological applications of a miniature microscope, the miniature microscope of the present invention can be used in endoscopes passed through small pipes, and for use in-situ observation during processing of semiconductors and other materials.
The present tendency is to carry out clinical procedures with small tools mounted in catheters, to make internal observations inside vessels with fiber optic devices, and to carry out operations using laser and fiber-optic techniques. Much less damage is done to the body than with older surgical methods by using such procedures. Observations of what is being done on a microscopic scale would be helpful, since the best resolution that presently can be obtained with endoscopes is of the order of 10-20 .mu.m. Another example is the observation of cancer cells in the uterus, where it is extremely painful to carry out biopsies. An in vivo imaging technique for this purpose which leaves the tissue intact would be a considerable improvement over present practice.
Several fiber optic microscopes have been suggested in the past, but either they are too bulky or too slow, so that the frame time is of the order of several seconds, or the definition is very poor.sup.1-6. Thus, these microscopes are not suitable for in vivo real-time imaging at the microscopic level.
We reported a vibrating fiber microscope in a recent paper.sup.7. A Fresnel lens made by photolithographic means was mounted on the end of a vibrating glass rod approximately 0.8 mm square. The lens was illuminated from an optical fiber glued to the other end of the rod, and formed a spot of the order of 1.8 .mu.m in diameter at an approximate distance of 1 mm from the lens. Light reflected from the object being observed was passed back through the fiber and lens to a detector. The signal from the detector, after suitable processing, was displayed through an image converter as a video image. The rectangular-shaped rod was vibrated by electrostatic fields, applied between it and an outer tube, at its slightly different mechanical resonant frequencies in the x and y directions. Hence, the focused spot from the lens formed a raster pattern (a Lissajous figure). The vibration frequencies were of the order of 8 kHz, and a single frame of the image took about 1/20 second to form. The resolution was about 2 .mu.m. This microscope suffered from the disadvantage that the vibrating rod needed support from a rigid and massive structure, which made the supporting structure large and unsuitable for use in the body.